A multicast or broadcast service (MBS) is a service that simultaneously transmits the same content to a plurality of users through single transmission. The MBS provides an efficient mechanism in an aspect of using broadcasting communication resources. While a technology for a wireless access has evolved for a fourth generation in mobile communication, the MBS is currently evaluated as a key technology. Service contents to be provided through the MBS henceforth and a data amount are expected to exponentially increase.
In a wireless section, the MBS simultaneously provides common content to mobile terminals using the same frequency and time resources. Considering mobility, a plurality of base stations is configured as a single common service zone, thereby decreasing sensitivity to user movement. That is, an MBS user may seamlessly use data of an MBS without a predetermined procedure while the MBS user moves through a plurality of cells. It is possible since the plurality of cells is allocated as a common service region called zone.
To minimize battery consumption, a terminal may shift to an idle state in which a predetermined portion of a radio channel is not decoded. Registration of an idle state terminal is released from a corresponding base station and the idle state terminal freely moves without connecting to a base station. In most MBS mechanisms, correlation between an idle state terminal and a base station is absent. However, a scheme of enabling the idle state terminal to continuously receive MBS data is applied.
One of the important concepts of the MBS is a macro-diversity characteristic. Macro-diversity enables a plurality of base station constituting the same MBS zone to transmit the same data to a terminal at the same point in time, thereby enabling the terminal to receive the same data from the plurality of base stations while the terminal is maintaining time synchronization with each base station. The terminal restores MBS data based on a different synchronization time with each base station. Since the terminal receives the same data from the plurality of base stations, a data decoding gain by macro-diversity is improved.
FIG. 1 is a diagram to describe the requisites to determine whether an idle state terminal is present within coverage of a multicast or broadcast service (MBS).
Referring to FIG. 2, The macro-diversity has disadvantages in a resource allocation aspect. To obtain a macro-diversity gain, all of the base stations belonging to the same zone need to transmit MBS data while using a predetermined amount of radio resources. Even though there is no terminal receiving MBS data from a predetermined base station belonging to a predetermined MBS zone, the corresponding base station may continuously transmit the MBS data. In this case, waste of radio resources occurs. Considering a tendency that an MBS data traffic amount continuously increases, a mechanism for solving the above issue is required.
To solve the above issue, there is a need to accurately verify the number of terminals that are in an idle state, while receiving MBS data. To solve the above issue, the conventional art induces an idle state terminal to be associated with a predetermined base station using a mechanism called paging. An idle state terminal of a macro-diversity operation mode receives MBS data from a plurality of base stations. Therefore, even after a paging process, a base station may arbitrarily perform dynamic resource allocation for corresponding MBS data.